[RFC 3/3] qom: Improve error message in module_object_class_by_name()

["Jose R. Ziviani" <jziviani@suse.de>]

module_object_class_by_name() calls module_load_qom_one if the object
is provided by a dynamically linked library. Such library might not be
available at this moment - for instance, it can be a package not yet
installed. Thus, instead of assert error messages, this patch outputs
more friendly messages.

Current error messages:
$ ./qemu-system-x86_64 -machine q35 -accel tcg -kernel /boot/vmlinuz
...
ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL)
Bail out! ERROR:../accel/accel-softmmu.c:82:accel_init_ops_interfaces: assertion failed: (ops != NULL)
[1]    31964 IOT instruction (core dumped)  ./qemu-system-x86_64 ...

New error message:
$ ./qemu-system-x86_64 -machine q35 -accel tcg -kernel /boot/vmlinuz
accel-tcg-x86_64 module is missing, install the package or config the library path correctly.

$ make check
...
Running test qtest-x86_64/test-filter-mirror
Running test qtest-x86_64/endianness-test
accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
accel-qtest-x86_64 module is missing, install the package or config the library path correctly.
accel-tcg-x86_64 module is missing, install the package or config the library path correctly.
...

Signed-off-by: Jose R. Ziviani <jziviani@suse.de>
---
 qom/object.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/qom/object.c b/qom/object.c
index 6a01d56546..2d40245af9 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1024,6 +1024,24 @@ ObjectClass *object_class_by_name(const char *typename)
     return type->class;
 }
 
+char *get_accel_module_name(const char *ac_name);
+
+char *get_accel_module_name(const char *ac_name)
+{
+    size_t len = strlen(ac_name);
+    char *module_name = NULL;
+
+    if (strncmp(ac_name, "tcg-accel-ops", len) == 0) {
+#ifdef CONFIG_TCG_MODULAR
+        module_name = g_strdup_printf("%s%s", "accel-tcg-", "x86_64");
+#endif
+    } else if (strncmp(ac_name, "qtest-accel-ops", len) == 0) {
+        module_name = g_strdup_printf("%s%s", "accel-qtest-", "x86_64");
+    }
+
+    return module_name;
+}
+
 ObjectClass *module_object_class_by_name(const char *typename)
 {
     ObjectClass *oc;
@@ -1031,8 +1049,20 @@ ObjectClass *module_object_class_by_name(const char *typename)
     oc = object_class_by_name(typename);
 #ifdef CONFIG_MODULES
     if (!oc) {
+        char *module_name;
         module_load_qom_one(typename);
         oc = object_class_by_name(typename);
+        module_name = get_accel_module_name(typename);
+        if (module_name) {
+            if (!module_is_loaded(module_name)) {
+                fprintf(stderr, "%s module is missing, install the "
+                                "package or config the library path "
+                                "correctly.\n", module_name);
+                g_free(module_name);
+                exit(1);
+            }
+            g_free(module_name);
+        }
     }
 #endif
     return oc;
-- 
2.32.0